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Na 0.5 Bi 0.5 TiO 3 -based ceramics are considered to be a prospective material for energy storage applications due to their unique phase transition and crystal structure. However, the large remanent polarization (P r) and coercive field (E c) limit their application in energy storage devices. In this work, the composition-dependent structure, dielectric properties and energy storage properties of Bi(Mg 2/3 Nb 1/3)O 3 (BMN) modified Na 0.5 Bi 0.5 TiO 3 -NaNbO 3 (NBTNN) ceramics were systematically investigated. The introduction of BMN promotes the formation of local random field, which effectively suppresses the hysteresis loss along with P r , and form "slender" P-E hysteresis loops. The maximum recoverable energy density of 5.26 J/cm3 is obtained in the optimum composition 0.8NBTNN-0.2BMN, which is about three times more than that of the undoped one, while yielding a high energy efficiency of 78%. In addition, the introduction of BMN into NBTNN ceramic results in excellent temperature stability and significant enhancement in band gap of the material. The improved energy storage performance of BMN modified NBTNN ceramic indicates their potential applicability in dielectric capacitors. • The introduction of BMN promotes the formation of local random field, and effectively suppresses the hysteresis loss. • (1- x)NBTNN- x NN ceramics exhibit wide bandgap, improved insulation properties and typical relaxor behavior. • The superior energy storage performance can be obtained in 0.8NBTNN-0.2BMN ceramics with W rec of 5.26 J/cm3 and η of 78%. [ABSTRACT FROM AUTHOR]

Dielectric capacitors have attracted considerable attention owing to their excellent performance, including high charge-discharge rate as well as good temperature stability and fatigue resistance. Na 0.5 Bi 0.5 TiO 3 (NBT)-based ceramics are considered to be one of the most prospective lead-free dielectric materials because of their unique phase transition and relaxation characteristics. However, the energy storage performance obtained in the currently available materials is not satisfactory. We propose a synergetic optimization strategy through composition design and domain engineering in 0.74Na 0.5 Bi 0.5 TiO 3 -0.26Sr 0.7 Bi 0.2 TiO 3 (NBSBT) ceramic, i.e., by simultaneously refining the grain size and widening the bandgap width, which facilitates a large breakdown strength and Δ P (P m – P r). A high dielectric constant and low remnant polarization is beneficial for obtaining improved energy storage properties. Piezoelectric force microscopy revealed that the introduction of NaNbO 3 (NN) disrupts the microdomains of the NBSBT ceramics and promotes the generation of polar nano-regions. An excellent energy storage density (W rec) of 4.83 J/cm3 and a moderate efficiency (η) of 87.4% are obtained at the optimum composition of 0.85NBSBT-0.15NN. These characteristics demonstrate that (1- x)NBSBT- x NN based ceramics are promising candidate materials for high-temperature energy storage devices and provide an effective strategy for the design of next-generation dielectric capacitors. [ABSTRACT FROM AUTHOR]

A novel ternary compound (1- x)(0.7BiFe 1- y Mn y O 3 -0.3BaTiO 3)- x KTaO 3 (BFMBT- x KT) is fabricated by solid-state synthesis technique. A systematic investigation of the crystal symmetry, ferroelectric properties, light absorption, and photostrictive properties was carried out with various Mn and KTaO 3 doping content. The phase transition behavior induced by the addition of KTaO 3 is investigated using X-ray diffraction and Rietveld refinement. The addition of KTaO 3 leads to the appearance of the tetragonal phase and the coexistence of pseudo-cubic and tetragonal phases. Furthermore, a high fraction of the tetragonal phase is obtained due to the increased KTaO 3 content. The solid solution BFMBT-0.02 KT exhibits strong ferroelectricity (P r ≈ 42 μC/cm2) as well as a narrow bandgap (E g ≈ 1.91 eV). Moreover, the largest photostriction of 1.68 × 10−3 has been achieved in BFMBT-0.02 KT under 405 nm laser irradiation. These improvements are strongly associated with the contribution of KTaO 3 -induced phase transition in ceramics. The power-dependent Raman spectroscopy reveals a redshift of phonon modes associated with B–O bond vibrations, indicating microscopic lattice expansion under illumination. As a result, the ternary BFMBT- x KT solid solutions with excellent photostriction will be a promising candidate for wireless optomechanical applications. [ABSTRACT FROM AUTHOR]